Compact polarized illuminators using reflective polarizers

Abstract

Projection systems and components thereof are described that are well suited to miniaturization. These systems and components may use one or more of the following features: a folded optical path, as in a reflective cavity or a beamsplitter; an illumination beam that is converging at the place where it impinges upon the spatial light modulator; a beamsplitter that uses opposed prisms of substantially different sizes; a beamsplitter whose obliquely disposed partial reflector defines a first rectangular reference space, and where at least a portion of the light source or at least a portion of the projector lens is disposed within such first rectangular reference space; a system in which a ratio of areas of the first rectangular reference space and a second rectangular reference space is within a specified range, where the second rectangular reference space is just large enough to encompass the optical components of the projector; a system in which the projector lens is small compared to the spatial light modulator.

The invention claimed is: 
     
       1. A compact polarized illuminator, comprising:
 a reflector; 
 a reflective polarizer disposed to form a reflective cavity with the reflector; 
 a retarder film disposed within the reflective cavity; and 
 a light source disposed to emit a polarized input light beam into the reflective cavity through an aperture in the reflector; 
 wherein the reflector, the reflective polarizer, and the retarder film are configured to produce an output illumination beam from the polarized input light beam, wherein the output illumination beam is polarized with a polarization type opposite to that of the polarized input light beam, and wherein at least one of the reflector and the reflective polarizer is curved, and wherein the output illumination beam is converging. 
 
     
     
       2. The compact polarized illuminator of  claim 1 , wherein light follows a light path from the light source to the output illumination beam that includes passing through the aperture, reflecting from the reflective polarizer, reflecting from the reflector, passing through the reflective polarizer, and passing at least two times through the retarder film. 
     
     
       3. The compact polarized illuminator of  claim 1 , wherein the reflective cavity defines a cavity volume, and a majority of the cavity volume comprises at least one solid light-transmissive material. 
     
     
       4. The compact polarized illuminator of  claim 1 , wherein the reflective cavity defines a cavity volume, and a majority of the cavity volume comprises air or vacuum. 
     
     
       5. The compact polarized illuminator of  claim 1 , wherein the retarder film is proximate the reflector, and the aperture is also in the retarder film. 
     
     
       6. The compact polarized illuminator of  claim 1 , wherein the illuminator further comprises a scattering element to make the output illumination beam more spatially uniform. 
     
     
       7. The compact polarized illuminator of  claim 6 , wherein the scattering element comprises a roughened surface, and the roughened surface is part of the reflective cavity. 
     
     
       8. The compact polarized illuminator of  claim 6 , wherein the scattering element comprises a layer of scattering material within the reflective cavity. 
     
     
       9. The compact polarized illuminator of  claim 1 , wherein the light source comprises an LED and a polarizer. 
     
     
       10. A projector, comprising:
 the compact polarized illuminator of  claim 1 ; 
 a spatial light modulator disposed to intercept the output illumination beam so as to produce a spatially patterned beam; and 
 a projector lens to receive the spatially patterned beam. 
 
     
     
       11. The projector of  claim 10 , wherein the spatial light modulator is a transmissive spatial light modulator. 
     
     
       12. The projector of  claim 10 , wherein the spatial light modulator is a reflective spatial light modulator. 
     
     
       13. The projector of  claim 10 , wherein the projector lens has a maximum lateral dimension LD 1  and the spatial light modulator has a maximum lateral dimension LD 2 , and wherein LD 1  is less than LD 2 . 
     
     
       14. The projector of  claim 10 , wherein the projector further comprises a detector to receive light originating from a body outside of the projector through the projector lens.